He is using fereakay time travel logic to suggest that the Loveletter comes from the future, is heeded by the past, thus rewriting the future, to retcon away the (to quote Mr. Dagon) "'Landfall destroyed Tamriel' interpretation of the Loveletter", which some people believe contradicts the 'only Morrowind' reality as presented by the novel.
Obviously if you don't believe that the Loveletter suggests Landfall destroyed all Tamriel, then there is no contradiction and no need for funky time-travel retcons.